Demonstration of the effect of ultrasonic cavitation on apoptosis induced by chlori̇ne E6 mediated sonodynamic therapy for PC3 cell line

Objective: Sonodynamic Therapy (SDT) as derived from Photodynamic Therapy is becoming increasingly important in cancer treatment. Its mechanism of action has not been fully elucidated, but revealing it would contribute to the positive outcome of the therapeatic process. This study aimed to determine the effect of one of the mechanisms called acustic cavitation on cell death triggered by SDT application. Material and Methods: PC3 prostate cancer cell line was used for in vitro SDT application. Total 105 cells per well were seeded in six-well plates. The sonosensitive agent Chlorin e6 was applied to the cells at a predetermined dose (5 µM). The cells were then exposed to ultrasound at a frequency of 1 MHz with varying intensity and duty cycles. The cavitation values formed in the medium containing the cells were measured. In order to determine the efficacy of SDT treatment, cell viability and metabolic activity were tested with 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazolyum bromür tetrazolyum assay (MTT) and Hoechst/ Propidium Iodide (HO/PI) stain. Measurements were recorded to relate with cavitation levels. Results: According to MTT findings, as the ultrasound duty cycle increased, the cavitation level elevated significantly and cell viability decreased significantly. Depending on the increase in ultrasound power density, cell viability decreased significantly, but the increase in cavitation levels was not stable. Conclusion: There is a relationship between cavitation level and SDT activity, but no increase in cavitation level was observed in all cases where cell viability was reduced. Exploring this negative effect on cell viability would require investigating other mechanisms of SDT action.